This invention relates to polymer stabilizer compositions comprising carbonate esters of cycloaliphatic dihydric alcohols and to certain novel carbonate esters of alkylidenebis dicyclohexanol compounds useful in stabilizer compositions for synthetic resins subject to deterioration on heating at 150.degree. C. or higher or on exposure to light of wave length shorter than 400 nanometers.
As a class, organic carbonate esters are well known, see for example the review by W. Tuemmler in Kirk-Othmer Encyclopedia of Chemical Technology, Second Edition, (J. Wiley-Interscience, New York 1964), vol. 4, pages 386 to 393. Organic dihydroxy compounds give either cyclic or polymeric carbonate esters depending on the number of carbon atoms between hydroxyl groups, and the pioneering studies on polymerization and ring formation by W. H. Carothers and coworkers included work with dihydric alcohol carbonates having molecular weights up to about 5000 (see J. Amer. Chem. Soc. 1930 Vol. 52 pages 314-326).
Carbonate esters of dihydric phenols are also well known. With molecular weights in the range of 10,000 to 100,000, preferably 18,000 and higher, carbonate esters of bisphenols having two benzenoid rings connected through a linking group such as alkylidene, cycloalkylidene, or sulfonyl constitute tough clear plastics useful in the forms of films, fibers, and molded articles. Much of the very extensive patent literature on thermoplastic carbonate polyesters has been summarized by L. Bottonbruch in "Encyclopedia of Polymer Science and Technology" (N. Bikales, ed., J. Wiley Interscience, New York 1969, vol. 10 pages 710-764).
There are only a few scattered mentions of carbonate esters of cycloaliphatic dihydric alcohols, M. Gawlak et al in "Chemistry and Industry" 1962, vol. 25, page 1148 have described the bis(ethyl carbonate) esters of the cis and trans/isomers of 2,2,4,4-tetramethylcyclobutane-1,3-diol and their conversion to high melting carbonate esters along with carbon dioxide and 2,2,4-trimethyl-3-pentenal. G. A. Adam et al in "European Polymer Journal," 1976, vol. 12, pages 295-298 have described carbonate esters of a mixture of 4,4'-isopropylidenediphenol and cyclohexane-1,4-dimethanol containing 1 to 52.9 mole percent of the cyclohexane dimethanol and having lower crystallinities and glass transition temperatures than the diphenol homopolymer.
Certain carbonate esters of polyhydric phenols having molecular weights well below the range useful for mechanical strength, i.e. not more than 10,000, have been disclosed as stabilizers for olefin polymers and other kinds of organic material subject to deterioration on heating.
D. Bown et al. in U.S. Pat. Nos. 3,510,507 of May 5, 1970 and 3,691,132 of Sept. 12, 1972 disclosed polyolefins stabilized with polyphosphites, polyphosphates, polyphosphonites, polyphosphonates, polyborates, polycarbonates, and polysilanes which are condensation products of a 4,4'-bisphenol with a condensing or linking agent which may be of the ester type, such as the esters of triaryl or mixed aryl-alkyl compounds, or the acid halide type. Bown's condensation product stabilizers have molecular weights between 600 and 8000 or higher and are described by the structural formula, ##STR3## where X is selected from the group consisting of ##STR4## where A is a C.sub.1 to C.sub.16 alkylene or an arylene; R', R", R'", and R"" are selected from the group consisting of hydrogen, C.sub.1 to C.sub.18 alkyls, and an aryl group; Y is selected from the group of ##STR5## where R is hydrogen, a C.sub.1 to C.sub.18 alkyl, or aryl; ##STR6## where m is 0 to 10, preferably 4 to 8, ##STR7## where A' is (CH.sub.2).sub.n --S--(CH.sub.2).sub.n or --(CH.sub.2).sub.n --S--(CH.sub.2).sub.m --S--(CH.sub.2).sub.n where n is 0 to 10, preferably 2 and m is 0 to 10, preferably 5; ##STR8## where R is an alkyl, preferably methyl, and Z is ##STR9## where R', R", R'", R"", and X correspond respectively to the R',R",R'",R"", and X previously selected when n has a value from 1 to 15, or Z may be derived from the compound used to introduce Y into the product when n has a value from 2 to 15, for example --R or --OR where R is hydrogen, an alkyl, or aryl. When Y in the formula of Bown's stabilizer is ##STR10## the stabilizer is a type of hydroxyaryl phosphite. Similarly, when Y in the formula is ##STR11## the stabilizer is a hydroxyaryl carbonate.
Bown's condensation products are described as especially effective in high molecular weight solid polyolefins when used together with a dialkyl sulfide costabilizer such as dilauryl thiodipropionate, distearyl thiodipropionate, ditridecyl thiodipropionate, dicetyl sulfide, bis(tetradecylmercapto) paraxylylene, and 10,24-dithiotetracontane.
J. Floyd et al in U.S. Pat. No. 4,032,510 of June 28, 1977 disclosed low molecular weight polycarbonate esters of bisphenols such as 2,2-bis(3-t-butyl-4-hydroxyphenylpropane) and 4,4'-butylidene bis(6-t-butyl-3-methylphenol) prepared in such a way as to contain few or no free phenolic hydroxyl groups as being highly effective heat and light stabilizers for polyolefins and giving a synergistic effect with distearyl thiodipropionate, tris (nonylphenyl) phosphite, and distearyl pentaerythritoldiphosphite.